U.S. Pat. No. 5,843,311(‘the 311 patent’) describes an analytical method and apparatus for extraction of organic analytes from a sample in a non-aqueous liquid organic solvent in an extraction cell in an oven under elevated temperatures and pressures below supercritical conditions. The method will be referred to as ‘accelerated solvent extraction’.
The organic solvent is pumped by a mechanical pump into the extraction cell with an open outlet and then the cell is closed and the system is pressurized under pump pressure. The cell is also heated in the oven to increase the pressure. Alternatively, the cell can be preheated prior to pumping the solvent into the cell. After extraction is complete, a purge gas supplied from a gas tank flows through the cell to displace the solvent containing the extracted analytes which flows to a collection vessel. U.S. Publication No. 2014/0063487 A1 (‘the '487 publication’), published Mar. 6, 2014, describes an improved accelerated solvent extraction system. It suggests at paragraph 21 that a compressed gas source may be used to pump the liquid solvent. It describes a restrictor tube 112 which generates back pressure sufficient to maintain the solvent in a liquid state. A commercial embodiment of an accelerated solvent extraction system is sold by Thermo Fisher Scientific under the trademark Dionex 350 Accelerated Solvent Extractor and is described in an Operator's Manual (Document No. 065220, Revision 4, December 2011). It includes a static valve between the extraction cell and collection vessel which opens when a predetermined pressure is exceeded.
These systems are significant improvements over the systems which had been used before them for extracting organic analytes from sample using organic solvents. However, there is a need to reduce the cost of the instruments and methods for performing these extractions and, specifically, to make a portable form of the instrument.